I am driving a 2006 XLE with 194000 miles. The following symptoms began showing this fall in order listed below. Note that all of this was preceded by a failed DRIVER SIDE TEMPERATURE CONTROL SERVO MOTOR that I tied up in the "HOT" position to accommodate colder weather. All problems listed below started after I made this change (the motor has been failed for more than a year; replacement is proving hard to find and costly - when flapper is tied in "cold" position, we get cold A/C generated air. When tied in "hot" we get hot - excepting for conditions stated below):
1. No heat. After initially demonstrating normal operation, the driver/passenger/rear regions would blow no hot air in cold weather. Occasionally, after long spells of operation blowing ice cold air (A/C off), hot air would emit from the ducts, but only for a short while.
2. De-frost fail. During these episodes and also during wet weather when the window shield is likely to fog over, the defrost would not blow hot air - it would add condensate to the window and make the problem worse (this was with and without A/C turned on, all temp settings).
3. Overheating. After about a month and no success finding solution, the van began to run hotter than normal, but not technically overheating (in red zone). discovered coolant was low - topped off, temperature back to normal for a while. Previous condition corrected temporarily.
4. Ka-blooey. All symptoms returned, getting ZERO heat - and in fact ICE COLD - from ducts when heat functions are on. It's almost like the heated coolant is not circulating. Van ultimately overheated and there was a blowout of radiator (crack was discovered). When this happened, temperature needle dropped to basement below zero and the dash lit up. (see pic taken AFTER/DURING severe overheating - this was when I discovered radiator crack after removing front grill) Reservoir was topped off but engine did not pull fluid from reservoir anymore. While the coolant is full and topped off, heat is fine all is fine. When level drops, everything goes to crap. No heat, no defrost, no nothing.
5. checked engine code. result = P0117.
Could the problem be as simple as the cracked radiator? ( i feel the crack resulted from a lack of flow and overheating and bloom-ee-loom)
Is it worth replacing the ECT and/or the thermostat? Where is the thermostat on this crazy vehicle?
Is the engine cooling issue related/connected to the Temperature Control Servo Motors for the cabin? (Driver side is currently removed, I think one more is bad but still installed - the one for the rear).